1. Field of the Invention
The present invention relates to electrostatic-capacitance-type acceleration sensors formed using semiconductor micro-machining technology.
2. Description of the Related Art
In such acceleration sensors, in order to suitably vibrate their movable electrodes, which are mass bodies constituting acceleration detectors, in a vacuum or inert gas, the acceleration detectors need to be sealed with a separator such as a glass cap; meanwhile, in order to output a signal, from the acceleration detectors installed inside the glass cap, to the exterior, wires also need to be provided passing through the separator.
Accordingly, an acceleration sensor is disclosed in Patent Document 1, in which a glass cap (cap) is anodically bonded to a bonding frame (frame) made of single-crystalline silicon in which impurities such as phosphorus are doped at a relatively low level, so as to form a tight-sealed space. That is, a bonding frame is formed of a high-resistant single-crystalline silicon layer provided on an insulating layer using a silicon oxide film, and also single-crystalline silicon layer of the same high-resistance is used as wirings, with impurities such as phosphorus being diffused.
[Patent Document 1]
Japanese Laid-Open Patent Publication 150,916/2000 (FIG. 2)